The present invention relates to a spray-coating powder facility.
Accordingly the invention relates to a spray-coating powder facility containing at least two powder stations per powder receptacle, at least one injection unit comprising at least one injector fitted with a powder pickup pipe which can be dipped into a powder container of the powder stations in order to aspirate from it powder to be conveyed to a receiver.
A spray-coating powder facility of this kind is known from EP 0 689 875 A2. It discloses an air injection unit fitted with several powder pickup pipes comprising an injector at their lower end. The injector unit is supported by a conveying system which may be in the form of a system with which to dip the powder pickup pipes into a powder receptacle, or of a robot fitted with a robot arm moving the injection unit into arbitrary (3D) directions.
However instead of configuring an injector at the lower end of a powder pickup pipe, it is more common practice to mount the injector at the upper end of the powder pickup pipe, for instance in the manner disclosed in DE 40 21 674 A1.
It is further practically known to configure the powder receptacles and their injection unit into an evacuation cabin from which air is aspirated by means of a blower and filter assembly. In this manner a slight partial vacuum is maintained in the evacuation cabin to prevent powder particles from leaking out of the evacuation cabin.
When changing pigments or powder (changing from one pigment to another), it is necessary not only to exchange the powder receptacles but furthermore all powder itineraries from the powder receptacle to the spray system also must be cleaned or exchanged. Cleaning is implemented using compressed air to blow clean the external surfaces of the powder itineraries and/or using compressed air which is blown through the inner paths, ordinarily through manually held compressed-air hoses.
The objective of the invention is to accelerate powder changing and to reduce the labor entailed in changing powders.
In the invention, the powder facility for spray coating is characterized in that it comprises at least one cleaning unit fitted with at least one compressed-air output matching an intake aperture at the lower pipe end of the powder pickup pipe in order to blow compressed cleaning air through the powder pickup tube and its injector and thus to clean them, further in that the minimum of one injection unit is displaceable in controlled manner relative to the powder stations and relative to the minimum of one cleaning unit in order to operationally connect the minimum of one injection unit alternatively to one of the powder stations or to the minimum of one cleaning unit, the minimum of one injection unit being controlled to alternatively dip by means of at least one powder pickup pipe into a receptacle of the powder stations for the purpose of conveying coating powder therefrom or in that said minimum of one injection unit being controlled to combine outside the receptacles with the cleaning unit for the purpose blowing compressed cleaning air through the minimum of one powder pickup pipe and its injector.
Accordingly the spray-coating powder facility may be designed in such a way that the powder stations and at least one cleaning unit shall be mutually fixed in place and in that the minimum of one injection unit shall be controlled to be displaceable in at least two and preferably three dimensions. This design offers the advantage that no drive system is needed for the heavy powder stations and that only stationary compressed air lines are needed for the cleaning unit.
Preferably the powder stations are arrayed in a straight or a circular line. This configuration simplifies the relative motions between the injection unit and the powder stations.
The minimum of one cleaning unit may be situated next to the line of powder stations. As a result, the displacement paths of the injection unit can be kept short. In another embodiment, one cleaning unit may be configured between every two or more powder stations. The displacement paths are shortened even more thereby.
In an especial embodiment, the powder stations can be controlled to move along a horizontal dimension of motion, namely the minimum of one injection unit being moved in controlled manner in a vertical dimension of motion, and the minimum of one cleaning unit shall be fixed in place within the dimension of motion of the powder stations. As a result the danger of supply line leaks shall be reduced because the pneumatic lines of the cleaning unit shall not be displaced and the injection unit need not be rotated at its pneumatic and powder lines.
The powder stations may be configured in a straight or circular line on a horizontally displaceable stage, where said line runs along the horizontal dimension of motion. In this manner the equipment of the invention may be matched to the spatial conditions at the site of application.
In a preferred embodiment the stage assumes the form of a turntable of which the center of rotation is situated at the center of the circular line of powder stations. Such a configuration is compact and its injection unit in it need not be rotatable.
In an especially preferred embodiment, the invention provides that the minimum of one cleaning unit shall be mounted underneath the stage on a base that is fixed relative to the stage and in that the stage shall comprise at least one vertical passage through which the minimum of one injection unit and the cleaning unit can be vertically joined to each other to be cleaned by the compressed cleaning air. This feature allows reducing the number of cleaning units, for instance to just one; this configuration is very compact; and the compressed air lines and the powder lines need not follow relative motions between the facility components. The cleaning unit may be vertically displaceable.
All embodiments preferably comprise a cleaning system for external surfaces fitted with at least one compressed-air nozzle by means of which compressed air can be blown on the external surfaces of parts of the injection unit, at least on the external surfaces of the powder pickup pipes, when the injection unit is situated opposite the cleaning unit. As a result, the coating powder is prevented from dropping from these external surfaces into a powder receptacle and from contaminating the coating powder in said receptacle.
Preferably the itinerary of the compressed cleaning air blown into the compressed-air cleaning pipe will run beyond the powder pickup pipe and its injector as far as the receiver. In this manner the powder line, usually a hose, need not be separately cleaned or exchanged when changing powders.
Powders can be changed in especially rapid manner and entailing little or no labor if, in the manner of the invention, an electronic control system is used that contains at least one computer program controlling the relative motions of the minimum of one injection unit, the powder stations and the minimum of one cleaning unit, further controlling powder conveyance, powder changes and cleaning using the compressed cleaning air. Preferably the control system shall be freely programmable as regards the computer program in order to allow speedily matching customer requirements.
At least the powder stations and the cleaning unit, but preferably also the injection unit and the moving systems for these stations and/or units shall preferably be mounted within an evacuation cabin fitted with a filter and blower system filtering and evacuating air out of the evacuation cabin into the environment. Coating powder is prevented thereby to reach the outside environment.
The filter and blower system sucks the air and powder inside the evacuation cabin preferably transversely to and through the powder stations arrayed in a line in order that no powder shall be transferred from powder station to powder station whereby otherwise different powders might be mixed.
The invention implements the following design:
(a) Preferably situated within an evacuation cabin, the powder facility comprises at least two powder stations resp. powder receptacles, at least one injection unit, at least one cleaning unit cleaning the injection unit using compressed air, a drive system to relatively move the injection unit, the powder receptacles and the cleaning unit, and an electronic control system controlling said motions and the operations of said parts, preferably as a function of one or more computer programs. The evacuation cabin contains one or more blower units with associated filters. These blower units generate a partial vacuum of such magnitude in the evacuation cabin that no powder or air may leak out said cabin into the external environment. Preferably the air inside the evacuation cabin is guided in such a way that the flow of air and powder in said cabin runs from the individual powder receptacles to the filters without thereby moving over other powder receptacles and consequently in a way to preclude contaminating powder pigments among the powder receptacles. Preferably the powder receptacles shall be separated by partitions.
(b) The injection unit may contain one or several injectors and can be displaced in controlled manner relative to the powder receptacles (powder stations) and to the cleaning unit. This operation can be implemented in several ways: the injection unit may be displaceable whereas the other components may be stationary; or the injection unit is stationary and the other two components are displaceable; or the powder receptacles (powder stations) are stationary and the injection unit and the cleaning unit are displaceable; or all three components are displaceable. A drive unit is provided for such purposes and is able to move the injection unit (or one and/or the other component xe2x80x9cpowder stations and/or cleaning unitxe2x80x9d) in two or more dimensions on several planes and at different speeds. The drive elements used for said drive unit may be elements of the state of the art, preferably electric and/or pneumatic drive elements.
(c) Preferably the cleaning unit shall be situated near the injection unit and may be in the form of one unit or several. This cleaning unit blows clean the injectors and their powder pickup pipes on the inside and preferably also on the outside. Moreover wiper pins or similar cleaning accessories may be used to clean the external surfaces of the injection unit.
(d) Preferable the powder receptacles shall be stationary and preferably they shall be controlled using fluidizing, vibrating, sifting, leveling and/or weighing units. The terminology used in the present patent that the powder receptacles, the injection unit and the cleaning unit are mutually displaceable, that is, that they are mounted in xe2x80x9cmovablexe2x80x9d or xe2x80x9cfixedxe2x80x9d manner, merely denotes mutual positioning displacements, but not vibrations or other motions leaving the relative positions of these parts unaffected. On that account a xe2x80x9cfixedxe2x80x9d powder station nevertheless may be fitted with a vibration unit to vibrate its power receptacle.
According to the invention, when there is a change from one powder receptacle to another, the injection unit may be automatically moved to the cleaning unit and be automatically cleaned at latter before proceeding to the other powder receptacle. The injection unit is dipped by its powder pickup pipes into the pertinent powder receptacle in order to pneumatically remove pigment from it and convey it to a spray system or a buffer container on the way to said system.